Screening Still the "Best Buy" for Tackling Cervical Cancer: In Spite of a Vaccine That Holds Some Promise for Cervical Cancer Prevention, Screening Is Still Essential. Debora Miranda Reports on the Options for Developing Countries
Miranda, Debora, Bulletin of the World Health Organization
When teenager Aisha received a vaccination against the human papillomavirus (HPV) at her school in Uganda, she knew more about cervical cancer than her classmates. Her mother had died of the disease, the second most common cancer in women in developing countries. Aisha's mother was one ofhalfa million women worldwide who are estimated to develop cervical cancer each year, more than half of them die as a result.
Virtually all (99%) cervical cancer cases are linked to infection with HPV. The majority of sexually active people will acquire HPV infection at some time in their life. Infection usually clears without treatment within a few months and does not cause any lasting problems. However, persistent infection of high-risk HPV types beyond 12 months is linked to an increased risk of cancer.
In 2006, the first vaccine to prevent the most common cancer-causing HPV infections became available. Since then, more than 120 countries have licensed the jab and 33 of them have introduced national vaccination programmes primarily targeted at adolescent girls like Aisha. However, even in these mainly high-income countries, a vaccination programme will not eliminate the need for screening because the current vaccines only protect against HPV types that are responsible for about 70% of cervical cancer cases. Because most people are infected with HPV early in their sexual lives, to achieve greatest impact young people need to be vaccinated before they are sexually active.
So this poses the question: should governments invest more in vaccination or screening?
Claudio Politi, health economist at WHO, says: "The difficult choice in a context of scarce resources is to identify the right balance. Investment strategies depend on the price of the vaccine, duration of vaccine protection, efficacy, the cost of screening and country resources such as trained professionals and treatment options."
Pap smears have been the standard screening procedure in the developed world for almost 50 years but they require quality laboratory services and an efficient infrastructure that allows rapid transport of smears. "There are not enough cytologists in developing countries" says Nathalie Broutet, medical officer at WHO.
Many African countries have opted for visual inspection with acetic acid (VIA), an inexpensive, low-tech test in which a health-care worker applies dilute acetic acid (vinegar) to the cervix and looks for abnormal tissue that temporarily turns white in contact with the vinegar.
Between 2005 and 2009, WHO and the International Agency for Research on Cancer were involved in implementing cervical cancer prevention and control programmes based on VIA followed by the use of cryotherapy for treatment where available, in six African countries: Malawi, Madagascar, Nigeria, Uganda, the United Republic of Tanzania and Zambia. More than 20 000 women have been screened so far and VIA is now included as part of cervical cancer screening in 17 national or regional programmes.
Nathalie Broutet, who coordinated the project, explains: "We should start to implement cervical cancer prevention and control programme with what is available, is not expensive and saves lives, such as VIA. Once you have the structure of a programme with all components in place, you can then improve the programme and consider changing the screening method with new ones that perform better and that will be, hopefully, soon on the market. …